I've been enjoying it: work with smart folks, occasionally speak at conferences, learn whatever you're curious about.. However, the money situation can become tricky (especially in New York). I double my income from summer internships but have still managed to accumulate a lot of credit card debt. I would recommend the lifestyle only if, in addition to having a good advisor/lab and liking open-ended exploration, you (1) are habitually frugal (2) go to school somewhere cheap or (3) have a big pile of savings.